78 THE NAUTILUS. 



Soft parts pink, especially so the foot and mantle edges; the liv- 

 ing mussel appears pale red ; but the color soon fades away after the 

 death of the animal ; it is also very pale, scarcely noticeable in the 

 young, becoming more intense with the age of the animal. 



Habitat: Maine, Rhode Island, Indiana, Illiouis and Minnesota; 

 probably also Utah, California and Washington. 



Pis. roperi can not be mistaken for any other species except some 

 forms of P. abditum Hald., but is at once distinguished from the 

 latter species by its comparatively very broad beaks, the more elon- 

 gated and more regular outline, the different appearance of its sur- 

 face, usually the lighter color, the comparatively finer and shorter 

 hinge, and, in the living animal, by the pink color of the soft parts, 

 shining through the shell. It is the only species in which that color 

 has been noticed so far, yet it remains to ascertain whether this be 

 a constant character. But, however that may be, the species is 

 valid. From several places specimens were obtained in company 

 with P. abditum, and at once recognized as distinct. It was first 

 noticed among Pisidia sent by Mr. E. W. Roper, in whose honor it 

 is named. The largest and most beautiful specimens were collected 

 in Higginbotham's spring, near Joliet, 111., by Messrs' J. H. Ferris 

 and G. H. Handwerk, who, from April, 1896, to this summer, re- 

 peatedly forwarded me lots of living specimens together with P. 

 abditum and another species. 



There are specimens from the Wasatch Mountains, Utah (sent by 

 Mr. Bryant Walker), the Sierra Nevada (Mr. Roper), and Seattle, 

 Wash. (Mr. P. B. Randolph), resembling the present species, 

 although somewhat different from it as well as among themselves, 

 and it is with some doubt that they were referred to P. roperi. 



Pis. fallax var. sepentrionale n. 



Differs from the type by the following characters: it is more 

 rounded in outline, less inflated, the beaks are less prominent and 

 without ridges ; the striation is less sharp; usually there are whitish 

 dots and irregular blotches, evidently caused by disease. 



This seems to be a northern form. Pine and Mountain Rivers on 

 the south shore of Lake Superior, collected by Mr. Bryant Walker ; 

 Clear Water River, Minn., in company with rather typical and in- 

 termediate specimens (Mr. H. E. Sargent), Little Madawaska River 

 at New Sweden, and Aroostook River at Caribou, Me. (Mr. Olof O. 

 Nylander), from the latter river in 1896 and '98, and there are 

 some specimens with distinct ridges on the beaks, or indications of 

 such. 



